Baby teeth offer hope for autism researchers

Updated 11:29 pm, Monday, July 23, 2012

Hoping to explore the potential links between autism and environmental exposure, a team of San Antonio scientists has found a new source of clues: in baby teeth.

In a new study, the researchers collected 21 molars lost by or extracted from young, healthy children at a local dental clinic. They ground them up and were able to detect exposure to medicines, pesticides and other chemicals — as well as the presence of fatty acids thought to protect against damage from those toxins.

The next step is collecting more lost baby teeth from 100 autistic and healthy children and seeing if any of those toxic exposures are linked to higher rates of autism.

“Most scientists agree now — probably 99.9 percent — that environment and genes play a role in autism,” said Raymond Palmer, a co-author of the study and associate professor of family medicine at the University of Texas Health Science Center. “But nobody knows what environment and what genes. So this is a big step in finding out what people have been exposed to during the critical periods of development.”

The advantages of looking for early exposures in baby teeth are many. In the first place, they're plentiful — it just requires swiping them from the tooth fairy. And there's lots of research showing exactly when and how each tooth is formed, both in the womb and in the first months after birth. So the presence of a toxin in a certain tooth or part of tooth can point to the point at which the exposure occurred.

“If you're looking at autism, you'd like to go back and look at when was the exposure: before birth, or in the early years when the autism might have developed,” said David Camann, a staff scientist at Southwest Research Institute and lead author of the study, which was printed in an environmental journal Wednesday. “And there has been no way to do that, but we thought the teeth might be a way to accomplish it.”

The idea isn't new. In the 1970s, Dr. Herbert Needleman of Harvard Medical School found a correlation between high lead levels in children's teeth and low IQ scores. His findings led to the elimination of lead in gasoline and paint.

But only in recent years have scientists had the tools to measure the more complex chemicals this way. And in the case of plastics and pesticides, what were measured in the children's teeth were breakdowns of the chemicals, rather than the chemicals themselves, Camann said.

In the new study, between 10 percent and 29 percent of the teeth had evidence of four different pesticide and plastics exposures — none of which had previously been detected in human teeth. Researchers said that finding wasn't alarming in itself because those chemicals are everywhere. The question is whether they play a larger role in causing autism in a genetically susceptible group, a question the researchers cannot answer yet.